EV (electric vehicle) News and Discussion

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#1956402 13-Feb-2018 15:51

wellygary:

MikeAqua:

Supposedly we are getting some double decker EV buses in Welly. I'll be interested to see (assuming it actually happens) what routes they go on.

Tranzit's Double decker EVs will run on the Island bay-Churton Park route from July. ( they are installing an overhead fast charger at the Island bay terminus)

Going up the gorge fully loaded in a howling NWester will be interesting thou

Double Deckers in Wellington are tunnel restricted so cannot be used on the Karori-Seatoun route...

Thanks for the info. I hadn't thought of the tunnel. Blindingly obvious now that you mention it () and rules out the Airport route as well.

Certainly the switch away from trolley buses has added to noise along those corridors.

Wrightspeed have gone back to the drawing board as of November.

Sigh.

Mike

wellygary

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#1956405 13-Feb-2018 15:54

MikeAqua:

Thanks for the info. I hadn't thought of the tunnel. Blindingly obvious now that you mention it () and rules out the Airport route as well.

Certainly the switch away from trolley buses has added to noise along those corridors.

Wrightspeed have gone back to the drawing board as of November.

Sigh.

The airport service will remain run by NZ bus ( and whoever buys them) as it is a non contracted commercial service... so their will be no change of bus fleet for that service (along with the other services NZ bus retain...

MikeAqua

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#1956452 13-Feb-2018 16:54

wellygary:

The airport service will remain run by NZ bus ( and whoever buys them) as it is a non contracted commercial service... so their will be no change of bus fleet for that service (along with the other services NZ bus retain...

Full EV could be a struggle for either of the Flyer routes anyway - due to the higher speed motorway stretch.

Mike

Aredwood

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#1956675 13-Feb-2018 22:59

MikeAqua:

Still not following ...

Are you saying that the charge rate of the battery creates an additional physical force or some sort of field the generator must overcome to turn?

Short answer - yes.

As you know - electricity is needed to recharge a battery. And if you get that power from a generator (which can be an electric motor running in reverse). If you try to increase the amount of power that you draw from a generator, the amount of twisting force (torque) required to keep it spinning at the same speed increases. Or if you can't increase the twisting force, You have to instead increase the RPM of the generator. In an older car, that doesn't have computer controlled idle speed, you can cause the idle RPM to change. Just by varying the electrical load on the alternator. And in some modern cars, the alternator itself is computer controlled. As by varying it's output, small gains in fuel economy can be achieved.

So in an electric car, regenerative braking is simply varying the electrical load on the generator (traction motor being used in reverse) based on how hard the driver is pressing the brake pedal. When the torque required to maintain the generator at a constant RPM, is higher than the contribution of gravity (due to the car going downhill). The generator starts to slow down (car goes slower).

Regen braking also makes it really easy to implement cruise control in an EV (which can both brake and accelerate to keep the car at a constant speed). As the control circuit just has to keep on moving power between the batteries and electric motor, to keep the car at a constant speed.

kingdragonfly

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#1957038 14-Feb-2018 13:07

I got a quote on the Tesla 3 demoed at Queensgate Wellington of over NZ $100,000.

People are budgeting around NZ $67,000 in the US.

Here's a recent article about pricing.

https://electrek.co/2018/02/11/teslas-delays-in-achieving-model-3s-35000-price-might-open-the-door-to-other-electric-cars/

"...Tesla received close to 500,000 reservations for the Model 3, which is impressive no matter how you look at it, but it’s not clear how many are only buying the least expensive version starting at [NZ $48,000].

A previous survey showed that the majority are actually budgeting closer to [NZ $69,000] for the Model 3.

But it still leaves a significant number of Model 3 reservation holders counting on the [NZ $48,000] base price.

In the US, some of them are even stretching their budget and counting on the [NZ $10,000] tax credit in order to buy the Model 3.

It’s them who are most affected by Tesla’s change last week that pushed standard battery pack production to ‘late 2018’.

The standard battery pack is essential for Tesla to reach the [NZ $48,000] price point since the current ‘Long Range’ battery pack in production adds a [NZ $12,000] premium on the vehicle"

Linuxluver

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#1957054 14-Feb-2018 13:32

MikeAqua:

wellygary:

The airport service will remain run by NZ bus ( and whoever buys them) as it is a non contracted commercial service... so their will be no change of bus fleet for that service (along with the other services NZ bus retain...

Full EV could be a struggle for either of the Flyer routes anyway - due to the higher speed motorway stretch.

A bus lane with an 80kph speed limit would address that. You often can't go any faster than that for more than a fraction of a minute anway.

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MikeAqua

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#1957059 14-Feb-2018 13:42

Aredwood:

Short answer - yes.

As you know - electricity is needed to recharge a battery. And if you get that power from a generator (which can be an electric motor running in reverse). If you try to increase the amount of power that you draw from a generator, the amount of twisting force (torque) required to keep it spinning at the same speed increases ...

So in an electric car, regenerative braking is simply varying the electrical load on the generator (traction motor being used in reverse) based on how hard the driver is pressing the brake pedal. When the torque required to maintain the generator at a constant RPM, is higher than the contribution of gravity (due to the car going downhill). The generator starts to slow down (car goes slower).

But how does it become more difficult to turn a generator with increased current draw. I guess this question is the reverse of how does a motor draw more power under increased load.

Is it to do with a change in the EM field(s) or something like that?

Mike

happyfunball

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#1957076 14-Feb-2018 14:06

Linuxluver:

Buses can carry 70 people in the space occupied by 3 cars....so buses won't be going away. Instead, what we might see is restrictions on the sort of silly behaviour @Aredwood (quitely right, IMHO) expects to be likely.

Buses are used by people because they are cheaper. When it costs the same to take an autonomous Taxi, who would take a bus?

Also, when a Taxi costs less than a bus, who would own a car and need to park it, or leave it driving around clogging up traffic?

The big auto companies are betting on fewer cars in the future, not more. Millennials are not buying cars like previous generations did. Ride hailing services are the next big growth area.

I think we're going to see fewer cars, buses, and traffic, but a lot more Ubers.

Rikkitic

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#1957077 14-Feb-2018 14:08

This is one of those sneaky questions that you think you know the answer to until you actually start thinking about it. My understanding is that drawing current creates a magnetic field in the opposite direction of the one that is generating the current. This acts as a brake. The bigger the load, the greater the drag created by the opposing field. To compensate, the generator (or engine driving it) has to speed up to deliver more power.

Plesse igmore amd axxept applogies in adbance fir anu typos

shk292

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#1957080 14-Feb-2018 14:12

MikeAqua:

But how does it become more difficult to turn a generator with increased current draw. I guess this question is the reverse of how does a motor draw more power under increased load.

Is it to do with a change in the EM field(s) or something like that?

I used to be able to explain this using electrical fields etc

But, to understand it simply, think of "you don't get anything for nothing" or the conservation of energy. If you increase the current draw from a generator, you increase the electrical power output (assuming constant voltage). This power has to come from somewhere - specifically the shaft - and as power is equal to rotational speed multiplied by torque, more current has to equal more torque.

wellygary

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#1957081 14-Feb-2018 14:14

kingdragonfly: I got a quote on the Tesla 3 demoed at Queensgate Wellington of over NZ $100,000.

But, what did they actually quote you on, there are so many different options available,

But as you say the minimum price on the current version runs to around 49K USD- (which would be around 80K NZD - but probably nearer 85K, (70c ex rate+15% GST)

-if you add the Autopilot and self drive options that runs to another 8K USD, so that bumps you pretty close to 100K..

The biggest problem I can see with Tesla pricing in NZ is that due to the market being very small, NZ motorists are very use to being presented with 2 or 3 spec levels of car that are imported by a dealer that they can get pretty much straight away,

NZ customers are not being faced with picking individual options (which add significantly to the "base" price and delivery time- esp if stock is not available....)

But I have still not heard when RHD model 3s are likely to be produced, personally I'm not expecting them until mid to late 2019... maybe even later....

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happyfunball

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#1957085 14-Feb-2018 14:17

MikeAqua:

But how does it become more difficult to turn a generator with increased current draw. I guess this question is the reverse of how does a motor draw more power under increased load.

Is it to do with a change in the EM field(s) or something like that?

Electromagnetism. More electricity, stronger magnets. Provide electricity to the motor and it will turn, more power, faster turning. Turn it the other way (against the direction of the magnets) requires torque but generates electricity. You can do this with those little electric motors in kids toys, turn them the other way and hook up a LED light to it, it will light up.

Its exactly how a power plant works, some kind of energy (usually steam turbines, or maybe a water wheel) turns a wheel which turns an electric generator. Turning the generator takes force and makes electricity. If you can turn the motor (generator) faster you get more electricity but its harder.

An EV uses your turning wheels to generate electricity instead of a water wheel.

MikeAqua

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#1957089 14-Feb-2018 14:22

Linuxluver:

A bus lane with an 80kph speed limit would address that. You often can't go any faster than that for more than a fraction of a minute anway.

That would have been a very sensible inclusion as an extra lane when they were redesigning to motorway. Would be a cluster- now.

But I'm sure the passengers on either of the 'Flyers' would prefer to be doing 100 where possible. They're supposed to be express services.

Raises an interesting question - can a bus that is entitled to use a bus lane where other lanes are available? I.e. leave a bus lane when traffic is light and use a faster lane?

Mike

MikeAqua

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#1957092 14-Feb-2018 14:25

happyfunball:

MikeAqua:

But how does it become more difficult to turn a generator with increased current draw. I guess this question is the reverse of how does a motor draw more power under increased load.

Is it to do with a change in the EM field(s) or something like that?

Electromagnetism. More electricity, stronger magnets. Provide electricity to the motor and it will turn, more power, faster turning. Turn it the other way (against the direction of the magnets) requires torque but generates electricity. You can do this with those little electric motors in kids toys, turn them the other way and hook up a LED light to it, it will light up.

Its exactly how a power plant works, some kind of energy (usually steam turbines, or maybe a water wheel) turns a wheel which turns an electric generator. Turning the generator takes force and makes electricity. If you can turn the motor (generator) faster you get more electricity but its harder.

I understand that a generator is just motor in reverse, but how does extra draw from the generator make it require more force to turn? Does it increase the strength of the magnetic field, making the rotor harder to turn?

Mike

Linuxluver

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#1957094 14-Feb-2018 14:30

happyfunball:

Linuxluver:

Buses can carry 70 people in the space occupied by 3 cars....so buses won't be going away. Instead, what we might see is restrictions on the sort of silly behaviour @Aredwood (quitely right, IMHO) expects to be likely.

Buses are used by people because they are cheaper. When it costs the same to take an autonomous Taxi, who would take a bus?

Also, when a Taxi costs less than a bus, who would own a car and need to park it, or leave it driving around clogging up traffic?

The big auto companies are betting on fewer cars in the future, not more. Millennials are not buying cars like previous generations did. Ride hailing services are the next big growth area.

I think we're going to see fewer cars, buses, and traffic, but a lot more Ubers.

You'll take a bus when a thousand Ubers can't get you there within an hour of when you'd like to get there.

Cars just do not scale. It's a physics thing. They take up a lot of space.

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